Twenty-one Florida-based banks were rated "zero" — the worst possible rating on a scale of zero to five stars — by the bank rating firm Bauer Financial Inc. In the previous quarter, ending Dec. 31, only 10 Florida banks were rated zero, a designation indicating weak capital and a high volume of bad loans.

The 21 zero-star banks are concentrated along Florida's gulf coast, most notably from Sarasota south to Naples. The locations of banks in greatest trouble mirror the state's worst housing markets, where foreclosures are highest and where price decline of homes for sale have been most severe.

There are exceptions. Other pockets of zero-star banks in Florida can be found in Miami and Panama City.

Customers of weak banks should monitor their progress and be sure their deposits do not exceed the current limits of federal deposit insurance. Specifics on those limits can be found online at the Federal Deposit Insurance Corp. Web site: www.fdic.gov.

The rapid increase of zero-star banks suggests Florida will see an increase in the pace of bank failures and federally orchestrated sales of weak institutions in the coming months and in 2010. Only three Florida banks have failed so far in 2009, though federal bank regulators have been busy in other parts of the country, notably in Georgia, closing and selling off troubled institutions.

None of Florida's zero-star banks are headquartered in the immediate Tampa Bay area. And some of them, such as Federal Trust Bank in Sanford and the Bank of Bonifay, have been sold to stronger institutions since March 31. But Sarasota's First State Bank operates a majority of its offices in Pinellas County.

Bauer Financial also rated 16 Florida banks with just one star, a sign that at least some additional banks may be poised to become zero-rated institutions later this year. In contrast, 18 Florida banks received five stars, including the First National Bank of Pasco in Dade City and Valrico State Bank in Valrico.